>> %vmstat -i
>> interrupt         count     rate
>> clk irq0       76952025       99

>And, having SOMETHING is far better than nothing.

Indeed.  It suggests this machine may be losing clock ticks.  Or
alternatively, truncation of a true clock rate rate somewhere between
99 and 100 is showing up, somewhat misleadingly, as 99.

If nothing else, I think an option to vmstat -i to show interrupt
rates in floating-point rate might be a useful improvment.